Add headless CMS for official site content management

Integrate article and page management into the Laravel admin dashboard
to serve as a headless CMS for the Next.js frontend (usher-site).

Backend:
- 7 migrations: article_categories, article_tags, articles, pivots, attachments, pages
- 5 models with relationships: Article, ArticleCategory, ArticleTag, ArticleAttachment, Page
- 4 admin controllers: articles (with publish/archive/pin), categories, tags, pages
- Admin views with EasyMDE markdown editor, multi-select categories/tags
- Navigation section "官網管理" in admin sidebar

API (v1):
- GET /api/v1/articles (filtered by type, category, tag, search; paginated)
- GET /api/v1/articles/{slug} (with related articles)
- GET /api/v1/categories
- GET /api/v1/pages/{slug} (with children)
- GET /api/v1/homepage (aggregated homepage data)
- Attachment download endpoint
- CORS configured for usher.org.tw, vercel.app, localhost:3000

Content migration:
- ImportHugoContent command: imports Hugo markdown files as articles/pages
- Successfully imported 27 articles, 17 categories, 11 tags, 9 pages

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/Http/Controllers/Api/ArticleController.php

@@ -0,0 +1,94 @@
+<?php
+
+namespace App\Http\Controllers\Api;
+
+use App\Http\Controllers\Controller;
+use App\Http\Resources\ArticleCollectionResource;
+use App\Http\Resources\ArticleResource;
+use App\Models\Article;
+use App\Models\ArticleAttachment;
+use Illuminate\Http\Request;
+use Illuminate\Support\Facades\Storage;
+
+class ArticleController extends Controller
+{
+    public function index(Request $request)
+    {
+        $query = Article::with(['categories', 'tags'])
+            ->active()
+            ->forAccessLevel()
+            ->orderByDesc('is_pinned')
+            ->orderByDesc('published_at');
+
+        if ($request->filled('type')) {
+            $query->byContentType($request->type);
+        }
+
+        if ($request->filled('category')) {
+            $query->whereHas('categories', function ($q) use ($request) {
+                $q->where('article_categories.slug', $request->category);
+            });
+        }
+
+        if ($request->filled('tag')) {
+            $query->whereHas('tags', function ($q) use ($request) {
+                $q->where('article_tags.slug', $request->tag);
+            });
+        }
+
+        if ($request->filled('search')) {
+            $search = $request->search;
+            $query->where(function ($q) use ($search) {
+                $q->where('title', 'like', "%{$search}%")
+                    ->orWhere('content', 'like', "%{$search}%");
+            });
+        }
+
+        $articles = $query->paginate($request->integer('per_page', 12));
+
+        return ArticleCollectionResource::collection($articles);
+    }
+
+    public function show(string $slug)
+    {
+        $article = Article::with(['categories', 'tags', 'attachments'])
+            ->active()
+            ->forAccessLevel()
+            ->where('slug', $slug)
+            ->firstOrFail();
+
+        $article->incrementViewCount();
+
+        // Get related articles (same content_type, excluding current)
+        $related = Article::active()
+            ->forAccessLevel()
+            ->where('content_type', $article->content_type)
+            ->where('id', '!=', $article->id)
+            ->orderByDesc('published_at')
+            ->limit(4)
+            ->get();
+
+        return response()->json([
+            'data' => new ArticleResource($article),
+            'related' => ArticleCollectionResource::collection($related),
+        ]);
+    }
+
+    public function downloadAttachment(string $slug, int $attachmentId)
+    {
+        $article = Article::active()
+            ->forAccessLevel()
+            ->where('slug', $slug)
+            ->firstOrFail();
+
+        $attachment = ArticleAttachment::where('article_id', $article->id)
+            ->findOrFail($attachmentId);
+
+        $attachment->incrementDownloadCount();
+
+        return Storage::disk('public')->download(
+            $attachment->file_path,
+            $attachment->original_filename
+        );
+    }
+}